I believe if you talk to most archery coaches, they would recommend you learn how to shoot properly (with back tension) from the get-go. Most archers pick up ALOT of bad habits (myself included) when starting with an index finger release, and as the years go by these bad habits are EXTREMELY hard to break. Learn correct form from the start, and you will be happier down the road. Ausie's suggestion of a thumb trigger model is a good one. I believe Carter makes a thumb trigger release where you can disable the trigger for a pure back tension release...this may be your best option, as you can then use it in a hunting situation with the thumb trigger.

Find a good pro-shop with a qualified archery instructor, and take a few lessons.

I would also recommend purchasing "Secrets from the Pros", which is a videotape by Carter archery that is very informative and can help anyone's shooting.